1. Field of the Invention
The present invention relates to a power management apparatus and a power management method, and a computer program product therefor, and relates particularly to a power management apparatus and a power management method, and a program therefor, for managing the total amount of power consumed by a computer group including a plurality of computers connected to a network.
2. Description of the Related Art
Recently, as transfer rates for the central processing units and the internal buses provided for computers interconnected by a network continue are increased, the number of transactions available for processing has increased sharply. Accordingly, there has been a proportional increase in the power required to perform the processing. Further, under conditions wherein only a limited quantity of power is available, throughput is reduced when the processing performed by central processing units is performed at rates that exceed a specific processing speed. This occurs when no mechanism is available for controlling the quantity of power required for the operation of the central processing unit of individual computers; and thus, when many transactions are to be handled by a specific computer, the main central processing unit of that computer cannot obtain the power required for its operation.
Furthermore, a computer can become inoperable when, due to an increase in the number of transactions handled, the amount of power consumed is excessive. This occurs because the quantity of the power supplied to each computer cannot be optimized, and excessive power may be consumed by a specific computer due to an increase in the number of transactions it executes.
A power management technique for a network computer, disclosed in Japanese Patent Laid-Open Publication No. Hei 04-100134, provides for the powering off of a computer when it is not currently in use, and thereby reduces operating costs. According to this technique, however, a computer that is not currently being employed is merely powered off, while the amount of power supplied to a computer that is currently being employed cannot be managed.
A technique, disclosed in Japanese Patent Laid-Open Publication No. 2003-122459, provides for the calculation of the total power consumption for a server system constituted by a plurality of sub-systems that include memories for storing information concerning power consumption. According to this system, power units connected to individual sub-systems supply power to the sub-systems. Server management cards connected to the individual servers extract the information concerning power consumption from the sub-systems, and based on the extracted information, calculate the total power consumed by the sub-systems. Since, however, this system employs the server management cards to calculate the total power consumption, a plurality of computers interconnected by a network can not manage power autonomously.